Cartridge feeding in a tubular magazine firearm



June 6, 1956 L. R. CRITTENDON ET AL 2,751,792

CARTRIDGE FEEDING IN A TUBULAR MAGAZINE FIREARM 4 Sheets-Sheet 1 Filed Jan. 19, 1955 INVENTORS l EX/E' IMY CK/TTENDO/V BY fLL/S W/LL/AM HA/LSTO/V June 1956 1.. R. CRITTENDON ET AL 2,751,702

CARTRIDGE FEEDING IN A TUBULAR MAGAZINE FIREARM 4 Sheets-Sheet 2 Filed Jan. 19, 1955 June 26, 1956 1.. R. CRITTENDON ET AL 2,

CARTRIDGE FEEDING IN A TUBULAR MAGAZINE FIREARM 4 Sheets-Sheet 3 Filed Jan. 19, 1955 L. R. CRITTENDON ET AL 2,751,702

June 26, 1956 CARTRIDGE FEEDING IN A TUBULAR MAGAZINE FIREARM 4 Sheets-Sheet 4 Filed Jan. 19, 1955 j F o IN VEN TORS CARTRIDGE FEEDING IN'A TUBULAR MAGAZINE FIREARM Claims. ((31. 42-47) This:invention relates to an improved breech loading magazine firearmof the type characterizedbya rearward v Theprincipal object of'this invention is toproVidetor improvements'in'the certaintyand accura'cy'with' which cartridgesare transferred from magazine to barrel cham= ber, thereby avoiding malfunctions due to failureto feed; etc.', and securingincreased accuracy through the avoidance'of bullet deformation on feeding,

Ainotherobject' is the provisionof improvedmeans for the manual operation of the rearwardsliding breech block and forsecurely locking such a breech block'inpositi'on toclosethebreech' end-of a barrel.

' Otherirnportantobjectives are'improvements 'in' safety, ir'r smoothness and speed of operation, and in economy or manufacture:

we contemplate that-we can best achieve=certain of these* objectives= by arranging our design to" utilize: to the maximum extent componentswhich are common to otherproduction firearms, for" example, the fire control assembl'y sh'ownin' U. S.- Patent No. 2,675,638, issuedon April 1-95'4; to-I R: Crittendon and utilized commercia'llyby applicants assig-uce in: an autoloa'ding shot gunga slide operated shotgun, and a slide operated center fi rarifle as well-as the presentdesign. Others of' th'ese objectives 1 are:achieved by: the-use of a die cast receiver so 'formedias :to avoiditheicomplicated .machine'ioperations usuallyirequiredltoicarve a=receiver out of "solidi-bar stock.

We contemplate? that: the important: functional ad vantages maybe. achieved by handling: the: cartridges throughiaseries of tpassageways .whichzmaintaimcomplete control; over the: cartridge: and: wev believe it to; be.- par; ticularly important that these passages: are fairlycloset in diameter to the largest diameter of the cartridge, obviating the chancefor cartridges tobecome misaligned.

We PIDVldBLflbl'flfiCh. boltwhich is. characterized by a cartridge head. engaging ,stem having an.outside diameter only. slightly, greater than the outside. diameter. of the.rim offthe. cartridge head. This'bol-t stem is. arrangedto. re .ciprocate. in aclosely fitting bolt stem guideway which is concentric with and'leads directly. into the chamber. of .theliarrela With the exceptionof an ejectionport the bolt stem guide way, closely surrounds a cartridge placed therein by hand-or throughfeedpassageways as. mentioned above. This arrangement insures that such a Qcartridge will be fed straight into the chamberi without opportunity .for the misalignment which, in conventional designs, sometimes results in the. cartridge Being "stemmed" or turned" crosswise across themouth of the chamber and'frequentlyresults in lead shaving or other deformationof the bullet.

we contemplatethat sucha bolt and cartridge feed mechanismiwill be useful both in blowbacki autoloading arms and'in manually operated arms. In the first caseit is necessary only to. couple to the bolt a bolt return springofsuitable characteristics andlettthe gas pressure exertedlonnthe head of a cartridge infiring providethe bolt opening force. In the second case it is necessary 2,751,702 Patented June. 26, 1956 to couple to the bolt a manual operating handle of somesort and to. provide for locking the-bolt in breech. closed position.

For. aamanually operated arm We provide a locking block. which. can be positioned. between locking surfaces on thebolt and. on the receiver and we utilize this locking blockas as means of coupling between the breech. bolt and. a manually operated action bar whichserves to lockand. unlock .thelockingcblock and to reciprocate the breech bolt.

The exact construction of a-preferred embodiment of our invention may be ascertainedby consideration of .the following detailed description referring to the attached drawings in .which:

Fig. 1 is. a: longitudinal vertical sectional. view taken through the action of a firearm embodying our invention. The mechanismis. shown inbreech closed positionwith thehammencocked but with the chamber empty andwith a column. of. cartridges in the. magazine.

Fig. 2:is-a..view-similar to. Fig- 1, with the. mechanism. showndn. breech open position ready to fecdacartridge to thechamber.

Fig.v 3 is a view similar to. Figs. 1 and 2,- with. the mechanismshown. in. partially. breech closedposition in theactoffeeding acartridge to the chamber.

Fig. 4 is a partialhorizontallongitudinal sectional .view on the.line...4.-4 of Fig. 1.

Fig. 5 is. a view similar. to Fig. 4, with.the breech mechanism just unlockedfrorn the receiver.

Fig; 6zis a vertical-cross=sectional .view onthe-1ine. 6-6 of:Fig. 1.

Fig. 7' is a vertical cross-sectionalview on theline7-7 of Fig. 1.

Fig. 8 isa vertical cross-sectional view on the line-.8-8 ofFig. 1.

' Fig. 9 is an enlarged. partial longitudinalvertical sectional view in the same plane as Fig. 1 but including only the barrel and receiver'tomoreclearly illustrate the cartridge feed passages.

Fig. 10'is a left hand elevational view-of the barreL-and breech bolt assembly.

Fig. 11' is an enlarged partial horizontal longitudinal sectional view on the line 4- and, except for the. enlarged scale, corresponds to a portion of Fig. 4.

Referring to the. drawings bycharacters of reference, it Wlllbfi seen that the invention is embodied in. a slide action magazine firearmhaving a barrel 1, a-receiver 2, and abuttstock 3 as basic structural units. A firecontrol assembly 4; conveniently that of thepatent abovereferred to. is supported in the. receiver and a breech bolt 5 is guided for reciprocation in the receiver. Beneath the barrell a conventional tubular magazineo is supported andaiore-end 7 is slidably supported thereon. action bars is provided to couple the slidable fore-end.to thebreech bolt, permitting manual operation. of .the action.

The receiver 2 of this constructionis conveniently v an aluminum die casting permitting a relatively intricate shape with a minimum of machining and with. great economy, in use of material since so little of the material need'be converted to useless chips in the manufacturing process.

The barrel 1 extends rearwardly into thereceiver to the-plane in which Fig. 6 is taken and is retained. there bya hardened takedown screw 9 passingthrough an cc.- centric hardened bushing 10 mountedin the forward ex.- tensionZa of the receiver and engaging a. hardened foreend hanger 11 secured rigidly to the barrel and providing aasupport for the rear end of the tubular magazine. By locatingthe hole for the takedown screw eccentrically inthebushing, a means. is provided for effecting. an initial 5y rotation of'the bushing, which adjustment may there- 3 after he maintained by staking the eccentric bushing in a fixed position in the receiver. The bushing also effectively increases the load bearing area of the aluminum receiver and insures that the receiver will not be deformed by loads encountered in use of the rifle.

The breech end of the barrel 1 is formed to define a bolt stern guideway 12 having a diameter only slightly, if at all, greater than the normal head diameter of the cartridges to be used therein and with the usual chamber 13 to support the cartridge during firing. The bolt is provided with a cartridge head engaging stem 14 which in the breech locked, or firing position shown in Figs. 1 and 4, substantially completely fills the bolt stem guideway and supports the head of a chambered cartridge. The means for locking and reciprocating the bolt will be separately discussed-below. The breech end of the barrel is also formed to define an ejection port 15 in alignment with an ejection port 16 in the receiver and communicating withthe bolt stem guideway. There are also formed in the breech end of the barrel certain cartridge feeding passages, also described in more detail later, which communicate between the bolt stem guideway and a track 17 formed in the receiver to receive cartridges urged by the magazine spring 18 and flexible follower 19 to pass from the breech end of the tubular magazine.

The fire control assembly 4 is described in detail in the patent referred to and will be only briefly referred to here. Its important elements are a hammer 20 controlled by a scar 21 and a trigger 22, the trigger being disconnected from the sear as a function of the fall of the hammer. An action bar lock 23 is also operated by the fall of the hammer and a manual release arm 24 is provided for the action bar lock, the function of the action bar lock being more fully described relative to breech bolt locking. The fire control assembly provides a convenient mounting base for a cartridge carrier 25 which is under the control of the breech bolt as will be described relative to cartridge feeding and is urged by a carrier spring 26 to assist in the feeding of a cartridge from the magazine to the chamber.

Cartridge feeding As best seen in Fig. 9, the cartridge feeding passages in the breech end of the barrel include an upwardly and rearwardly extending groove 27 which together with the track 17 formed in the receiver define an upwardly and rearwardly extending passage receiving cartridges from the tubular magazine and intersecting the bolt stem guideway to an extent such that an arcuate upper portion of the head of the rearmost cartridge in the passage can project slightly into the lower portion of the bolt stern guideway in the path of the bolt stem. Extending forwardly from the intersection of the groove 27 with the bolt stern guideway is a slot 28 which at its front end 28a and rear end 28b is defined by planar walls separated by a space greater than the diameter of the body of a rimmed cartridge but less than the head diameter thereof. The mid-portion of the slot has a width slightly greater than cartridge head diameter and is defined by a pair of part circular cuts defining opposed forwardly and upwardly inclined tracks 29 which will engage the rim on the head of a cartridge and raise it upwardly under complete control as the cartridge is pushed forwardly.

The receiver is vertically slotted through the bottom of the track 17 to permit movement of the carrier 25 upward and into the cartridge feeding passages. It will be noted that a cam lug 30 is provided on the carrier which is overridden by the enlarged head of the bolt 5 so that the carrier is depressed whenever the breech bolt is substantially in its locked position and at all other times is urged upwardly to the extent permitted by the cartridge in the feed passages. An abutment 31 is formed on the carrier to define the rearmost position which the head of a cartridge may reach, which position is not particularly critical provided the head is then to the rear of the enlarged mid-portion of the slot 28 and capable of being raised by the carrier into a position partially intersecting the path of the bolt stem. Obviously that portion of the carrier forward of the abutment 31 should not be longer than the shortest cartridge to be fed from the magazine. An abutment 32 is also formed by the tip of the carrier to oppose rearward movement of following cartridges while one is being fed to the chamber. A detent notch 31a receives the rim of a cartridge and assists in control thereof, as will be later described.

Considering the operation of the cartridge feeding mechanism, we may logically start with Fig. 1 in which the breech is closed on an empty chamber and a cartridge 33 is in the feed passages followed by a cartridge 34 under the urging of the magazine spring. As the bolt is moved rearwardly to the Fig. 2 position, the carrier is freed from restraint by the bolt and urges the head of the cartridge 33 upwardly to the maximum extent permitted by the narrow rearward portion 28b of the slot 28. The engagement of the rim of the cartridge in the detent notch 31a serves as a means of positively preventing an upward displacement of the bullet end of a short cartridge. At the same time, the body and bullet portion of the cartridge are inclined upwardly in the forward narrow portion 28a of the slot and the forward end of the carrier cuts off further movement by the cartridge 34.

As the breech bolt is moved forwardly the bolt stem picks up the projecting arcuate portion of the rim of the cartridge 33 and moves that cartridge forwardly in the slot 28. During this forward movement the enlarged rim at the head of the cartridge encounters the forwardly and upwardly inclined tracks 29 and, with the assistance of the carrier 25, the cartridge head is raised thereby up the face of the bolt stem in position for the rim to be engaged by the claws of the opposed extractors 35 in the bolt stem. As the carrier and the tracks 29 elevate the head of the cartridge, the carrier maintains a lifting pressure on the body of the cartridge, with the result that the cartridge is elevated smoothly and in a substantially continuous controlled movement is presented to the chamber in a straight line and without bullet deformation. Because the passages confine the cartridge quite closely there is no opportunity for a bullet to turn upwardly or crosswise and fail to enter or stem the chamber. Fig. 3 illustrates the relationship of the parts about halfway through the cartridge feeding operation.

As the bolt stern seats the cartridge 33 in the chamber the carrier is cammed downwardly by the bolt 5, releasing the following cartridge 34 to the position occupied in Fig. 1 by the cartridge 33.

Bolt reciprocation and locking As previously noted, a slidable fore-end 7 and action bar'8 are provided to reciprocate the bolt 5 in the receiver. Considering first Fig. 10 which shows the barrel assembly after the rifle has been taken down, it will be noted that the action bar extends rearwardly beneath the left hand side of the barrel to a position where it is normally guided by a track 36 formed in the receiver casting. At the rear end of the action bar an upstanding lug 37 is provided which is received in a semi-circular camming cut 38 in the outer face of a locking block 39. The locking block is received in a groove 40 of roughly dovetail shape extending vertically across the left hand side of the bolt body. The inner face of the locking block (see Figs. 4, 5, and 11) is defined by two flat portions 41 and 42 'at an angle to each other, the apex of that angle forming a center of rotation about which the locking block may rock. In the Fig. 4 and Fig. 11 or locked position, the forward flat portion 41 of the locking block lies on the bottom of the bolt groove and the curved surface 43 of the locking block is received in a locking recess 44 in the receiver side wall, forming a. strut which securely holds the bolt against any rearward locking'recess 44 is formed, the receiver forces the kick ingblock .to remain confined within thebolt groove, vthe engagement of the lug 3Ton the action .bar with the semi circular camming cut-38in the lockingiblock provides. a connection for. reciprocating. the. bolt.

Iii. the locked. position offFig. 4, .the. lug,.37' is. forward of the cammingcut 38, .bearing .on-.the. surfaceA-la and securely. holding. thelocking blockicin. locked position, but after a short.rearwardittavelcf: the. action. bar .the lug, enters the cannning cut 38 and bears .on therear curved surface thereof, camming the lockingqblockback into the bolt groove. On the return movement of the bolt theelug-gbcars on .th'e:forward'icurved-surface of the camming cut-38 and .as soonasrthe-lock-ingblock is opposite the locking recess 44 in the receiver, a component of theforce exerted-bythe-lug37 acts-to swingftthe'tail of therblockoutwardly; positioning -tlie"surface43" within the locking-recess 44- and 'retaining itthere when the lug 37"rids forwardly-out'of" the'camming' cut 38"onto1"the surface" 41a2' At least-"theoretically 'it would'seem desirable to" form the curved end 43 of the locking block to a radius of curvature identical with that of the locking recess 44. In practice, however, we have found that the locking block tends to indent itself minutely into the surface of the locking recess under the strain imposed by firing the more powerful cartridges. As a result, when the curvature of the surfaces is identical, it is sometimes difiicult to unlock the action. We have found that it is desirable to employ a slightly longer radius of curvature for the surface 43 and to center this radius on a line somewhat outside but parallel to the intersection of the planar surfaces 41 and 42, as best shown in Fig. 11. With this relationship every increment of rotation of the locking block about the intersection of the surfaces 41 and 42 tending to unlock the breech results not only in sliding movement of the surface 43 across that of the locking recess 44 but also results in a radial separation of those surfaces making unlocking quite easy. Similarly, upon locking, these surfaces tend to approach each other more closely and the breech bolt is cammed forwardly to its final closed position.

For best results, it is desirable to pre-load the locking system by firing a cartridge or by any other convenient means, to impress or pre-set the locking block in the recess 44, and then to set the rifle head space to desired standards by adjustment of the eccentric bushing 10 which is thereafter staked in place. With this procedure we have found that head space is maintained within acceptable limits throughout endurance tests involving the firing of many more rounds of ammunition than an average shooter can be expected to expend throughout the period of his use of a rifle.

The difference in the radius of curvature of the surface 43 and of the locking recess 44 is not particularly critical provided the relative relationships indicated above are maintained and further provided that the increase in the radius of curvature of the surface 43 is not so great as to result in an excessive concentration of the locking block load adjacent the corner 44:: of the locking block recess. A cutter run-out resulting in a tangential departure of the corner 44a from the right circular conformation of the rest of the recess 44 is heipflll in alleviating any tendency to upset in this region of the receiver and makes it easier to approach the theoretically perfect mating surfaces while maintaining the above described relationship which provides for easy openings.

When the rifle is taken down as in Fig. 10, the locking block is retained in the bolt groove by virtue of the dovetail shape" of" the bolt groove; the forward wall ofwhich may" be substantially" a right circular" cylindrical surfa'cedefined by. a radius ofthe lengthofthefiatsurfaee 41; Similarly; the .rear wallof thetbolt groove may be substantially a' right". circular, cylindrical surfaccgde'fined by a .radiusof the length'of'the flat surface 42 of the locking;.block,' andlthe: locking block tail 43asbears on this surface, being'limited in theextent of movement pcr= mittedby a lip 43b which is turned in to' obstructthle path of the tail; 43a. The locking block is retained against accidental removalfrorn' either. end. of the bolt groove by means 'of a hole45 passing through theflockr' ing block andljloosely embracing a pin 46.seated .in the bolt body. To'rernove thebolt' 5; from the assembly of Fig. 10, it is onlynecessary to spring the actionbarlateF ally to force it from the bolt groove and manually remove the bolt, such springing being performed without sub= stantialstrain' on the action bar which isthen' deprived of the support of its guide track 36,?in the receiver;

The action bar lock 23 previously referredto' engages in the conventional way with an abutment 47 "on the action bar when'the bolt is in locked. position .to releasablylock the bolt closed. Upon firing, as describedin the patent, the action bar lock isreleased by the fall ofthe hammer, permitting instant reloading by pumping the fore-end. Manualrelease of the actionbar lock is providediby, the action b'ar release lever 24; permitting unloading without firing or opening of the action for cleaning or inspection.

For completeness it may be noted that the bolt stem is longitudinally grooved to receive a firing pin 48, the rear end of the firing pin being exposed in a slot 49 in the bolt to the blow of the hammer 20. A post ejector 50, Figs. 4, S, and 6, is provided in the bolt stem guideway to intercept the head of a cartridge being extracted and to slip it laterally out of the ejection ports 15 and 16. A portion of the bottom of the receiver casting may be conveniently closed by a receiver cover 51 retained by the reception of spring tabs 52 in a groove cut in the inside wall of the receiver.

To insure that the bolt always looks up in the same orientation, we provide a bolt guide pin 53 seated in the receiver and engaging a slot 54 in the top of the bolt to prevent rotation of the bolt upon its own axis as it approaches the locked position. Without this more exact orientation, there might be some tendency for the locking block to engage at an angle and exert excessive unit pressure in some small element of the locking recess 44.

Although the detailed description thus far has dealt specifically with a slide action manually operated arm, it should be obvious that many of the components would be applicable to other forms of operation. For example, if the locking block and action bar lock were removed from the arm and the action bar coupled at one end directly to the bolt and at the other end to a breech closing spring instead of a manually slidable fore-end, all other elements could remain the same and the arm would function as a blowback operated autoloader. Obviously, the interchangeability of parts between two such companion models results in great economy in manufacture. The claims appended hereto are not therefore to be construed as limited solely to a manually operated firearm but to extend as well to blowback gas operation, and other applicable operating systems.

What is claimed is: I

1. In a firearm adapted for cartridges comprising head rims of a diameter greater than body diameter, the combination comprising a receiver; a barrel having therein a bolt stern guideway of a diameter not substantially greater than cartridge rim diameter; a bolt reciprocable in said receiver and having a cartridge head engaging stem slidable in said guideway; a tubular magazine adapted to contain a column of cartridges; spring-urged cartridge following means in said magazine; a cartridge receiving passage in said barrel and receiver communicating with said magazine, extending rearwardly and upwardly therefrom and intersecting said bolt stem receiving guideway whereby when said bolt stem is retracted in said guideway the head of the rearrnost cartridge in said passage partially projects into said guideway in the path of forward movement of said bolt stern; a slot in said barrel joining said passage and said bolt stem guideway, said slot having a length greater than cartridge length, having end porions of a width greater than cartridge body diameter and less than cartridge head diameter, and having a mid portion of a width greater than cartridge head diameter shaped to define a pair of opposed forwardly and upwardly inclined tracks whereby a cartridge engaged by said bolt stern in its forward movement is moved forward and upward through said slot and into said guideway.

, 2. The combination described in claim 1, including in said receiver a cartridge carrier engageable with the body of a cartridge in said cartridge receiving passage and spring-urged upwardly to urge the body of a cartridge upwardly through said slot.

3. The combination described in claim 2, said cartridge carrier being formed to define a magazine cut-off surface which, when said carrier is in raised position, obstructs rearward passage in said cartridge receiving passage of a cartridge following that raised by the carrier, and interengaging cam means on said carrier and on said bolt formed to permit said carrier to be raised by the spring when the bolt stem is retracted in the guideway and to positively depress said carrier when the bolt stern has substantially completed its forward movement in said guideway, thereby permitting said following cartridge to pass rearwardlyin said cartridge receiving passage into position to be raised by a subsequent operation of the carrier.

4. The combination described in claim 3, said receiver being formed to define a longitudinally and vertically extending slot intersecting said cartridge receiving passage through which slot said carrier may be raised and lowered.

5. The combination described in claim 4, said carrier being shaped to define a cartridge stop surface projecting into said cartridge receiving passage in the lowered position of the carrier in position to engage the head of the rearmost cartridge in said cartridge receiving passage and act as a positioning stop therefor.

References Cited in the file of this patent UNITED STATES PATENTS 2,369,244 Lowe Feb. 13, 1945 2,422,301 Horan June 17, 1947 2,577,026 Maillard Dec. 4, 1951 2,601,808 Clarke July 1, 1952 2,679,123 Williams May 25, 1954 2,679,124 Sefried May 25. 1954 

